1. Field of the Invention
The present invention relates to a producing method for a substrate for an electronic device having a conductive member on a surface, and a cleaning apparatus. In particular, it relates to a producing method for an image display apparatus having a conductor on a surface and such an image display apparatus, and more particularly to a producing method for an image display apparatus utilizing an electron beam such as a field emission display (FED) and such an image display apparatus.
2. Related Background Art
Non-patent Literature 1 describes a technology in which conductive particles execute a reciprocating motion between electrodes and go out of the electrodes.
Also a method of moving dusts is described in Patent Literatures 1 and 2, utilizing the technology disclosed in Non-patent Literature 1.
Also in image display apparatuses including cathode ray tube (CRT), developments are being made for realizing a larger image size.
Also a thinner structure, a lower weight and a lower cost are becoming important issues with an increase in the image size.
However, a CRT, in which electrons accelerated with a high voltage are deflected by deflecting electrodes for exciting a phosphor on a face plate, basically requires a larger depth in case of a larger image size and is difficult to provide a product of a small thickness and a low weight.
The present inventors have made investigations, as an image display apparatus capable of resolving the aforementioned limitations, on a surface conduction electron emitting device and an image display apparatus utilizing such surface conduction electron emitting device.
The present inventors have tried an application of multi electron beam sources as shown in FIG. 14.
In FIG. 14, there are schematically illustrated surface conduction electron emitting devices 4101, column wirings 4102 and row wirings 4103 which constitute multiple electron beam sources wired in a simple matrix configuration.
FIG. 14 also shows a structure of a cathode ray tube (also represented as image display panel) utilizing such multi electron beam sources, constituted of a substrate 4001 (also represented as rear plate) of an outer envelope provided with electron emitting devices 4101, row wirings 4102 and row wirings 4103, a lateral wall 4003 (also represented as supporting frame or outer envelope frame), and a face plate 4002 provided with a phosphor layer 4201 and a metal back 4203.
A phosphor layer 4201 on the face plate 4002 is provided with a phosphor for emitting light by an excitation with electrons, and a black matrix for suppressing a reflection of an external light and for avoiding color mixing of the phosphors.
The phosphor layer 4201 and the metal back 4203 are given a high voltage through a high voltage terminal 4005 and constitute an anode electrode.
In such image display apparatus, a high voltage (also represented as an accelerating voltage or an anode voltage) is applied to the metal back 4203 constituting a part of the anode electrode, to generate an electric field between the rear plate 4001 and the face plate 4002, thereby accelerating the electrons emitted from the electron beam sources and exciting the phosphor to cause a light emission and an image display.
As the luminance of an image display apparatus is significantly dependent on the accelerating voltage, the accelerating voltage has to be elevated in order to achieve a high luminance.
Also in order to realize a thin image display apparatus, it is necessary to reduce the thickness of the image display panel, and, for this purpose, the distance between the rear plate 4001 and the face plate 4002 has to be made small.
Because of these facts, a considerably high electric field is generated between the rear plate 4001 and the face plate 4002.                Patent Literature 1: Japanese Patent Application Laid-Open No. H08-100256        Patent Literature 2: Japanese Patent Application Laid-Open No. 2002-083542        Non-Patent Literature 1: IEEE Transactions on Dielectrics and Electrical Insulation, vol. 8, No. 4; August 2002.        Patent Literature 1 discloses, for eliminating dusts, a method of eliminating dusts deposited on a deposition preventing plate in a film forming apparatus such as a sputtering apparatus.        
In such method, very large dusts, for example those having a size of 100 μm or larger, can easily be liberated from an electrode and can initiate a reciprocating motion because of a large charge amount leading to a large Coulomb force acting on the particles.
However, small dusts or small unnecessary structural fragments (such as burrs) are not easily liberated by the Coulomb force and cannot therefore be removed.
An object of the present invention is to clean such small dusts or small unnecessary structural fragments that are difficult to remove with the Coulomb force only.
Also as an object of cleaning, the substrate of a flat panel display requires a cleaning for following reasons, and the present invention can be advantageously utilized for obtaining a flat panel display of excellent characteristics.
FIG. 15 is a schematic cross-sectional view of the above-described display panel.
The image display apparatus (flat panel display) is provided with a rear plate 4001 having an electron beam source and a face plate 4002 having a metal back 4203 constituting an anode electrode, to which an accelerating voltage Va is applied.
The anode electrode 4203 is insulated from the electron beam source by a vacuum gap between the face plate 4002 and the rear plate 4001.
A dimension of the vacuum gap defines a depth of the image display panel and is therefore preferably made smaller.
However, a smaller depth of the display panel, with a same voltage applied to the anode electrode 4203, results in an increase in the electric field intensity which is defined by dividing such voltage with the distance, thereby increasing a probability of causing a discharge between the anode electrode 4203 and the electron beam source.
Such discharge may significantly deteriorate the image quality of the image display apparatus, thus giving a major difficulty in improving the reliability of the image display apparatus.
Following three causes are conceivable for a discharge in vacuum: (1) an electron emission is caused by a concentration of electric field on a minute projection present on a cathode (rear plate in the present case), and the minute projection is heated by a Joule's heat of a current flowing in the minute projection (cathode heating assumption), thereby inducing a discharge; (2) an opposed anode (face plate in the present case) is heated by electron collision (anode heating assumption), thereby inducing a discharge; (3) clumps or minute dusts sticking to the electrode are liberated and accelerated by an electrostatic force and collide with an electrode to cause a heating of the electrode or the minute dusts, thereby leading to a discharge (clump assumption).
Also in case of increasing the area size of the image display panel, an increase in the area size tends to cause following two situations in the manufacturing process: (4) a defect in the form of a minute projection, directly leading to a discharge, is generated in the display panel; and (5) fragments (dusts) generated by a fragmenting of a conductive substance from a member constituting the display panel contaminate the panel.
Therefore, with an increase in the size of the display panel, influence of the discharge caused by the minute projections and the dusts becomes more important.
Therefore, an object of the present invention is to provide, for application to the aforementioned image display apparatus, a substrate for a flat panel display free from causes of discharge thereby providing a flat panel display of excellent characteristics having a low probability of discharge.
The present invention provides a technology capable, instead of the technology disclosed in Patent Literature 1 in which the conductive particles are charged, liberated and put into a reciprocating motion in a passive manner, of introducing desired particles between the substrates and moving such particles by an electric field thereby forcedly causing dusts sticking to the substrate to initiate a reciprocating motion and also destructing and removing substances of a projecting form.